Upgraded maven-scala-plugin to 2.15.2 with notes for 2.15.3
Upgraded maven-scala-plugin to 2.15.2 with notes for 2.15.3

ccagnoli/gremlin,tinkerpop/gremlin,cesarmarinhorj/gremlin,samanalysis/gremlin,tinkerpop/gremlin,ccagnoli/gremlin,samanalysis/gremlin,cesarmarinhorj/gremlin